ITEM:

INFORMATIONAL ITEMS/STAFF REPORTS

 

32.

QUARTERLY IRRIGATION PROGRAM AND RIPARIAN PROJECTS REPORT

 

Meeting Date:

January 24, 2008

Budgeted

N/A

 

From:

David A. Berger,

Program/

N/A

 

General Manager

Line Item No.:

 

Prepared By:

Thomas Christensen

Cost Estimate:

N/A

 

General Counsel Approval:  N/A

Committee Recommendation:  N/A

CEQA Compliance:  N/A

 

IRRIGATION OF RIPARIAN VEGETATION: The supplemental watering of riparian restoration plantings resumed in April of 2007 at eleven Monterey Peninsula Water Management District (District) riparian habitat restoration sites.  The following irrigation systems were in use during the period April through November: DeDampierre, Trail and Saddle Club, Scarlett, Begonia, Schulte South, Schulte Bridge, Schulte, All Saints, Valley Hills, San Carlos, and Dow.

 

            Water Use in Acre-Feet (AF)

            (preliminary values subject to revision)

           

            January - March 2007              0.09 AF

            April - June 2007                     1.25

            July – September 2007 6.95

            October – December 2007       3.37

            Total in 2007                            11.66 AF

 

MONITORING OF RIPARIAN VEGETATION:  During the months of May through October 2007, staff recorded weekly observations of canopy vigor on target willow and cottonwood trees to provide an indication of plant water stress and corresponding soil moisture levels.  Four locations (Rancho Cańada, San Carlos, Valley Hills, and Schulte) are monitored every week for canopy ratings based on a scale from one to eleven.  This scale evaluates characteristics such as yellowing leaves and percentages of defoliation (see scale on Exhibit 32-A).  A total of 10 willows and 9 cottonwoods at these locations provide a data set of established and planted sample trees that are representative of trees in the Carmel River riparian corridor.  Soil moisture measurements are conducted at three of these sites (San Carlos, Valley Hills, and Schulte) using tensiometers.  Soil moisture values are measured at seven stations with 18-inch and 36-inch tensiometers in the soil column.  Combined with monthly readings from the District’s array of monitoring wells and pumping records for large-capacity Carmel Valley wells in the Cal-Am system, the District’s monitoring provides insight into the status of soil moisture through the riparian corridor.

 

Current monitoring results for the 2007 monitoring season to date show that riparian vegetation has experienced moisture stress in some areas.  Signs of yellowing and defoliation up to 30% for willows and up to 10% for cottonwoods occurred this fall, but the overall riparian corridor still shows resilience given the critically dry year.  The graphs in Exhibit 32-A and 32-B show average canopy ratings for willows and cottonwoods in selected restoration sites in the lower Carmel Valley and impacts to water table elevations.

 

The types of monitoring measurements made during May through October 2007 are as follows:

 

            Monitoring Measurement                                        

 

            Canopy Ratings                                                (See Exhibit 32-A for trends.) 

            Soil moisture (tensiometers)                                         

            Groundwater levels (monitoring wells)   (See Exhibit 32-B for trends.) 

            Groundwater pumping (production wells)                     

           

 

OTHER TASKS PERFORMED SINCE OCTOBER’S 2007 REPORT:

 


1.         Vegetation Management on the Carmel River: District staff completed two weeks of successful “vegetation management” work along the Carmel River starting on September 18 and ending on October 3, 2007.  Vegetation was selectively removed from  three critical areas with vegetation encroachment in the channel bottom.  These sites were chosen for their potential to direct high flows from the center of the channel toward the banks and potentially cause erosion and property damage.

 

2.         Steelhead Barrier Modification in the Upper Carmel RiverOn December 5, 2007, District and California Department of Fish and Game staff members cleared a channel through a rock slide in the Carmel River above Los Padres Reservoir.  The clearing will enable steelhead to migrate through the slide area.  The rock slide was determined to be a steelhead migration barrier after a preliminary assessment in August 2007.   Approximately 50% of the Carmel River’s spawning habitat is estimated to be located above Los Padres Reservoir.

 

3.         San Carlos Irrigation System:  On December 17, 2007, District staff (Christensen, Hamilton, Bekker, and Lyons) removed the temporary irrigation system from San Carlos Road Bridge downstream past CAW's San Carlos Well (1,770 feet).  This system is designed to water riparian plants on the bank of the Carmel River to help alleviate moisture stress associated with groundwater pumping.  This system was removed because trees had gone dormant for the winter and recent rains have increased soil moisture.      

 

EXHIBITS

32-A    Average Willow and Cottonwood Canopy Rating

32-B    Depth to Groundwater

 

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